On 09/06/2016 12:54 PM, Bin Cheng wrote:
Hi, LOOP_VINFO_NITERS is computed as LOOP_VINFO_NITERSM1 + 1, which could overflow in loop niters' type. Vectorizer needs to generate more code computing vectorized niters if overflow does happen. However, For common loops, there is no overflow actually, this patch tries to prove the no-overflow information and use that to improve code generation. At the moment, no-overflow information comes either from loop niter analysis, or the truth that we know loop is peeled for non-zero iterations in prologue peeling. For the latter case, it doesn't matter if the original LOOP_VINFO_NITERS overflows or not, because computation LOOP_VINFO_NITERS - LOOP_VINFO_PEELING_FOR_ALIGNMENT cancels the overflow by underflow.Thanks, bin 2016-09-01 Bin Cheng <bin.ch...@arm.com> * tree-vect-loop.c (loop_niters_no_overflow): New func. (vect_transform_loop): Call loop_niters_no_overflow. Pass the no-overflow information to vect_do_peeling_for_loop_bound and vect_gen_vector_loop_niters.
OK when prereqs are all approved. jeff
